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An Intraoperative Crisis =================================================================== A case discussion on rising ETCO₂, hyperthermia, and tachycardia during emergency surgery [ MDster Editorial Team ](https://mdster.com/about) · Oct 20, 2026 · 6 min read · 30 [ Reviewed by Dr. Ali Ragab, MBBCH, MSc, MCAI ](https://mdster.com/medical-reviewers/dr-ali-ragab) [Editorial Policy](https://mdster.com/editorial-policy) | [Corrections Policy](https://mdster.com/corrections) [ Anesthesiology ](https://mdster.com/blog?tag=anesthesiology) [ Malignant Hyperthermia ](https://mdster.com/blog?tag=malignant-hyperthermia) [ Emergency Anesthesia ](https://mdster.com/blog?tag=emergency-anesthesia) [ Thyroid storm ](https://mdster.com/blog?tag=thyroid-storm) [ Case Discussion ](https://mdster.com/blog?tag=case-discussion) ![Thyroid Storm or Malignant Hyperthermia? An Intraoperative Crisis](https://mdster.com/storage/blog/images/thyroid-storm-or-malignant-hyperthermia-an-intraoperative-crisis.png) Share this article Share this post On this page 1. [ Two crises, one monitor pattern ](#two-crises-one-monitor-pattern) 2. [ What the history explains—and what it does not ](#what-the-history-explains-and-what-it-does-not) 3. [ Protect the patient before resolving the diagnosis ](#protect-the-patient-before-resolving-the-diagnosis) 4. [ The first minutes ](#the-first-minutes) 5. [ If thyroid storm is established or strongly suspected ](#if-thyroid-storm-is-established-or-strongly-suspected) 6. [ Target hormone action, synthesis, and release ](#target-hormone-action-synthesis-and-release) 7. [ ICU handover and clinical application ](#icu-handover-and-clinical-application) 8. [ Watch for a second cardiovascular crisis ](#watch-for-a-second-cardiovascular-crisis) 9. [ Key Points for Board Exams ](#key-points-for-board-exams) 10. [ Conclusion ](#conclusion) 11. [ Frequently Asked Questions ](#blog-faqs) 12. [ References ](#references-heading) On this page 1. [ Two crises, one monitor pattern ](#two-crises-one-monitor-pattern) 2. [ What the history explains—and what it does not ](#what-the-history-explains-and-what-it-does-not) 3. [ Protect the patient before resolving the diagnosis ](#protect-the-patient-before-resolving-the-diagnosis) 4. [ The first minutes ](#the-first-minutes) 5. [ If thyroid storm is established or strongly suspected ](#if-thyroid-storm-is-established-or-strongly-suspected) 6. [ Target hormone action, synthesis, and release ](#target-hormone-action-synthesis-and-release) 7. [ ICU handover and clinical application ](#icu-handover-and-clinical-application) 8. [ Watch for a second cardiovascular crisis ](#watch-for-a-second-cardiovascular-crisis) 9. [ Key Points for Board Exams ](#key-points-for-board-exams) 10. [ Conclusion ](#conclusion) 11. [ Frequently Asked Questions ](#blog-faqs) 12. [ References ](#references-heading) Thirty minutes into an emergency laparoscopic appendectomy, a 34-year-old woman’s heart rate reaches 155 bpm, ETCO₂ rises from 35 to 55 mmHg, and temperature climbs to 39.8°C. She has untreated Graves’ disease and received sevoflurane. **Thyroid storm is plausible, but malignant hyperthermia (MH) must be treated as an immediate threat.** Two crises, one monitor pattern ------------------------------- ### What the history explains—and what it does not Medication nonadherence, vomiting, infection, and surgical stress make thyroid storm credible. Excess thyroid hormone amplifies cardiovascular responses and increases metabolic demand; anesthesia can conceal the agitation or altered mental status that would help establish systemic decompensation. Storm remains a clinical diagnosis, supported rather than determined by scoring systems or hormone concentrations. [\[1\]](#cite-1 "Reference [1]") Sevoflurane, conversely, is an MH trigger. An inappropriate ETCO₂ rise may be an early sign of skeletal-muscle hypermetabolism; rapid temperature rise, hyperkalemia, and rhabdomyolysis can follow. Rocuronium may obscure rigidity, and a negative family history does not exclude MH. [\[2\]](#cite-2 "Reference [2]") PossibilityFinding that shifts suspicionMHPersistent hypercarbia despite increased ventilation, especially with mixed acidosis, hyperkalemia, or markedly rising CKThyroid stormSevere thyrotoxicosis with otherwise unexplained cardiovascular, thermal, or gastrointestinal decompensationSepsis or laparoscopic CO₂ absorptionInfection or insufflation-related hypercarbia; neither alone should readily explain a rapidly escalating hypermetabolic crisis The strongest discriminator here is **unexplained CO₂ production accompanied by evolving acidosis and muscle injury**, not temperature alone. Check the circuit, minute ventilation, insufflation conditions, and anesthetic depth—but do so alongside crisis treatment, not before it. [\[2\]](#cite-2 "Reference [2]") Protect the patient before resolving the diagnosis -------------------------------------------------- ### The first minutes 1. Declare an emergency, call for anesthesia help and the MH cart, and tell the surgeon to pause or end the procedure if feasible. 2. Stop sevoflurane. Deliver 100% oxygen at high fresh-gas flow, increase minute ventilation, and continue with nontriggering IV anesthesia. Use activated charcoal filters if available; do not delay treatment to change the anesthesia machine. 3. Begin active cooling and assess circulation. Obtain an ABG, potassium, glucose, lactate, CK, renal studies, and ECG; trend core temperature and urine output. Send TSH, free T₄, and T₃, but do not wait for results. [\[2\]](#cite-2 "Reference [2]") If MH remains a credible explanation, give **dantrolene promptly**: an initial 2.5 mg/kg IV is 150 mg for this 60-kg patient. Repeat according to clinical response and the local MH protocol. Cooling and ventilation are supportive; neither replaces dantrolene. Treat suspected thyroid storm concurrently when indicated rather than requiring certainty about a single diagnosis. [\[3\]](#cite-3 "Reference [3]") > **Clinical Pearl:** A rising ETCO₂ during laparoscopy may reflect absorbed insufflation gas. Persistence despite ventilation changes—particularly with rapid hyperthermia or acidosis—demands an MH response. [\[2\]](#cite-2 "Reference [2]") If thyroid storm is established or strongly suspected ----------------------------------------------------- ### Target hormone action, synthesis, and release The 2026 European-led thyroid-storm consensus supports coordinated critical-care treatment with beta-blockade, an antithyroid drug, corticosteroids, and appropriately timed iodide. Address the precipitant, including possible appendiceal infection, while restoring volume and managing temperature. Avoid treating an isolated heart-rate number without assessing perfusion and ventricular function. [\[4\]](#cite-4 "Reference [4]") - **Beta-blockade:** Titrate IV esmolol to clinical response when circulation permits. Its short action is useful if occult thyrotoxic cardiomyopathy or hypovolemia makes beta-blockade poorly tolerated. Propranolol is another option and, at higher doses, also reduces peripheral T₄-to-T₃ conversion. [\[4\]](#cite-4 "Reference [4]") - **Antithyroid therapy:** Give methimazole or propylthiouracil (PTU) enterally, including by NG tube when appropriate, to inhibit new hormone synthesis. PTU also reduces peripheral conversion, but current consensus finds no clear mortality advantage over methimazole; hepatic dysfunction weighs against PTU. [\[4\]](#cite-4 "Reference [4]") - **Iodide:** In Graves’ disease, give potassium iodide or Lugol’s solution **at least one hour after** the antithyroid drug. This limits release of stored hormone without supplying iodine before synthesis is blocked. [\[4\]](#cite-4 "Reference [4]") - **Corticosteroids:** IV hydrocortisone reduces peripheral T₄-to-T₃ conversion and provides coverage for possible relative adrenal insufficiency. The 2026 consensus describes a 100-mg IV loading dose followed by 50 mg every six hours. [\[4\]](#cite-4 "Reference [4]") Propofol is appropriate for nontriggering maintenance, but do not infer its required infusion rate from tachycardia alone. A small pharmacokinetic study found increased propofol clearance and distribution volume in hyperthyroid patients; titrate anesthesia to the whole clinical picture while investigating the metabolic crisis. Avoid agents likely to intensify sympathetic stimulation when suitable alternatives exist. [\[5\]](#cite-5 "Reference [5]") ICU handover and clinical application ------------------------------------- ### Watch for a second cardiovascular crisis Handover should state both the working diagnosis **and whether MH was treated or remains unresolved**. Report ETCO₂ and temperature trajectories, ABG and potassium results, CK trend, dantrolene exposure, ventilation and cooling, endocrine drug doses, and the time iodide becomes due. Request endocrine and critical-care review; continue surveillance for cardiac failure, arrhythmia, renal injury, and recurrent MH if suspected. [\[2\]](#cite-2 "Reference [2]") If atrial fibrillation with rapid ventricular response develops, first determine whether the patient is unstable. A stable patient may receive carefully titrated beta-blockade if perfusion allows; hemodynamic instability attributable to AF calls for immediate synchronized cardioversion. ICU discharge depends on sustained thermal and cardiovascular stability, improving organ dysfunction, and a workable ongoing treatment plan—not a universal heart-rate cutoff. [\[6\]](#cite-6 "Reference [6]") Key Points for Board Exams -------------------------- - Untreated Graves’ disease raises suspicion for storm; volatile exposure and disproportionate hypercarbia demand parallel consideration of MH. - Stop the volatile, ventilate with 100% oxygen, summon help, and administer dantrolene promptly when MH is suspected. - Use antithyroid therapy **before** iodide; titrate beta-blockade to perfusion, not a fixed heart-rate target. - Under anesthesia, neither absent agitation nor absent observed rigidity reliably settles the differential. Conclusion ---------- The decisive skill is managing diagnostic uncertainty without losing time. Protect against MH immediately, investigate the competing causes of hypermetabolism, and treat likely thyroid storm through coordinated endocrine and critical-care care. [\[2\]](#cite-2 "Reference [2]") Frequently Asked Questions ---------------------------- ### Should thyroid test results be available before treating suspected storm? No. Send thyroid studies, but begin treatment when the clinical picture strongly supports storm; results do not establish its severity. [\[1\]](#cite-1 "Reference [1]") ### Does rocuronium rule out malignant hyperthermia? No. Sevoflurane remains a trigger, and neuromuscular blockade may make rigidity difficult to recognize. [\[2\]](#cite-2 "Reference [2]") ### When should iodide follow an antithyroid drug? Wait at least one hour after administering the antithyroid drug before giving iodide for Graves-related storm. [\[4\]](#cite-4 "Reference [4]") ### What changes management if postoperative AF causes hemodynamic instability? Hemodynamic instability attributable to AF calls for immediate synchronized cardioversion rather than relying on pharmacologic rate control. [\[6\]](#cite-6 "Reference [6]") References (6) ------------------ 1. 1. [ American Thyroid Association. Guidelines for Diagnosis and Management of Hyperthyroidism, 2016. ](https://doi.org/10.1089/thy.2016.0229) [↩](#cite-ref-1-1 "Back to text") 2. 2. [ European Malignant Hyperthermia Group. Recognising and managing a malignant hyperthermia crisis, 2024. ](https://www.emhg.org/recommendations-1/2024/11/4/recognising-and-managing-a-malignant-hyperthermia-crisis-v2024) [↩](#cite-ref-2-1 "Back to text") 3. 3. [ Malignant Hyperthermia Association of the United States. Managing a Crisis. ](https://www.mhaus.org/healthcare-professionals/managing-a-crisis/) [↩](#cite-ref-3-1 "Back to text") 4. 4. [ European-led joint consensus statement on management of thyroid storm. European Thyroid Journal, 2026. ](https://pmc.ncbi.nlm.nih.gov/articles/PMC13506520/) [↩](#cite-ref-4-1 "Back to text") 5. 5. [ pubmed.ncbi.nlm.nih.gov/9661573 ](https://pubmed.ncbi.nlm.nih.gov/9661573/) [↩](#cite-ref-5-1 "Back to text") 6. 6. [ ACC/AHA/ACCP/HRS. Guideline for the Diagnosis and Management of Atrial Fibrillation, 2023. ](https://www.jacc.org/doi/10.1016/j.jacc.2023.08.017) [↩](#cite-ref-6-1 "Back to text") Study pathway Build momentum in Anesthesiology with focused, exam‑style practice -------------------------------------------------------------------- - Airway, ventilation, and crisis drills - High‑yield anesthesia pharmacology made practical - Track weak topics and improve faster Free 5-day trial No credit card required. [ Start practicing ](https://mdster.com/user/dashboard) [ Explore Anesthesiology ](https://mdster.com/speciality/anesthesiology) [ View pricing ](https://mdster.com/pricing) [ Explore features ](https://mdster.com/features) No credit card required. 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